1. Field of the Invention
The present invention relates to a solenoid valve device, and particularly to a solenoid valve which actuates an engine valve by an armature attracted by an electromagnet.
2. Description of the Related Art
Conventionally, as disclosed in Japanese Laid-Open Patent Application No. 7-332044, there is known a solenoid valve having an engine valve which functions as an intake valve or an exhaust valve of an internal combustion engine. In this solenoid valve, an armature is connected to the engine valve, and electromagnets are disposed above and below the armature, respectively. The electromagnets exert electromagnetic forces on the armature in a valve-closing direction and a valve-opening direction, respectively. The engine valve is so constructed that it is seated on a valve seat provided to a cylinder head of the engine when the armature is in contact with the electromagnet for closing. Thus, according to the above-mentioned conventional solenoid valve, the engine valve can be moved between a fully opened position and a fully closed position by alternately energizing the electromagnets.
Generally, the cylinder head of the engine is heated to a high temperature in association with combustion in a combustion chamber. Thus, the engine valve is also heated to a high temperature by heat transferred from the cylinder head. In this case, the cylinder head and the engine valve thermally expand to different extents due to a difference in a thermal capacity and a thermal expansion coefficient. If the engine valve thermally expands to a greater extent than the cylinder head, the engine valve may not be seated on the valve seat when the armature is in contact with the electromagnet for closing. In this case, a clearance is generated between the engine valve and the valve seat. Similarly, when the valve seat or the engine valve is worn away, the engine valve may not be seated on the valve seat.
It is a first object of the present invention to provide a solenoid valve device which can positively actuate an engine valve between a fully closed position and a fully opened position without formation of a clearance between the engine valve and an armature.
It is a second object of the present invention to properly control a current supplied to an electromagnet of the solenoid valve device.
The first object of the present invention can be achieved by a solenoid valve device, comprising:
an engine valve which can move in an axial direction thereof;
an armature which moves with the engine valve;
an electromagnet which attracts the engine valve so that the engine valve moves in the axial direction; and
a zero-lash adjuster mechanism which is interposed between the engine valve and the armature.
In this invention, the zero-lash adjuster mechanism is interposed between the engine valve and the armature. Thus, a change in a spacing between the engine valve and the armature can be compensated for by the zero-lash adjuster mechanism so that formation of a clearance between the engine valve can be prevented. Therefore, according to this invention, it is possible to positively actuate the engine valve while preventing formation of a clearance between the armature and the engine valve. When there is no clearance between the armature and the engine valve, the armature does not impact on the engine valve when the engine valve is actuated. Thus, according to the present invention, it is also possible to reduce an operating sound of the solenoid valve.
In this case, the zero-lash adjuster mechanism may be a displacement-compensating mechanism which can expand in accordance with an increase in a spacing between the engine valve and the armature.
In this invention, an increase in the spacing between the engine valve and the armature can be compensated for by an expansion of the zero-lash adjuster mechanism. Thus, formation of a clearance between the engine valve can be prevented irrespective of a change in the spacing therebetween. Therefore, according to this invention, it is possible to positively actuate the engine valve while reducing an operating sound of the solenoid valve device.
In this case, the displacement-compensating mechanism may be constituted so that it can expand when the engine valve is in a closed position.
In this invention, the displacement-compensating mechanism can expand when the engine valve is in a closed position. A change in a spacing between the engine valve and the armature is generated when the engine valve reaches a closed position. Thus, formation of a clearance between the engine valve and the armature can be effectively prevented by the displacement-compensating mechanism expanding when the engine valve is in a closed position.
In the solenoid valve device of the present invention, at least part of the displacement-compensating mechanism may be disposed inside the electromagnet.
In this invention, since at least a part of the displacement-compensating mechanism is disposed inside the electromagnet, a total height of the solenoid valve device need not be enlarged by a full height of the displacement-compensating mechanism. Thus, according to this invention, it is possible to reduce the total height of the solenoid valve device.
Additionally, in the solenoid valve device of the present invention, the zero-lash adjuster mechanism may comprise:
a displacement-compensating mechanism which can expand when no compressing force is exerted thereon;
a swing arm which is connected to one end of the displacement-compensating mechanism so that the swing arm can swing around the one end and is in contact with both the armature and the engine valve so that the armature moves in a valve-closing direction when the displacement-compensating mechanism expands.
In this invention, in a state where the engine valve is opened, the armature exerts a force on the swing arm in the valve-opening direction. Since the swing arm is in contact with both the armature and the engine valve so that the armature moves in the valve-closing direction when the displacement-compensating mechanism expands, the force exerted on the swing arm in the valve-opening direction by the armature is transmitted to the displacement-compensating mechanism as a compressing force. In this case, the displacement-compensating mechanism is not allowed.
On the other hand, in a state where the engine valve is closed, the armature does not exert a force on the swing arm in the valve-opening direction. In this case, the displacement-compensating mechanism is allowed to expand since no compressing force is exerted thereon. Thus, when a spacing between the engine valve and the armature increases, that is, when the armature shifts in the valve-closing direction relative to the engine valve, in a state where the engine valve is closed, the displacement-compensating mechanism expands so that the swing arm swings so as to maintain a state in which the swing arm is in contact with both the armature and the engine valve.
In this way, formation of a clearance between the engine valve and the armature can be prevented. Additionally, since only the swing arm moves in accordance of a movement of the engine valve and the displacement-compensating mechanism is maintained still, a mass of a movable part of the solenoid valve device can be reduced. Thus, according to this invention, it is possible to improve a response of the solenoid valve device.
Additionally, the displacement-compensating mechanism may be a hydraulic zero-lash adjuster which can expand by being supplied with an oil pressure.
In this case, the solenoid valve device may further comprise an oil pressure supplying mechanism for supplying an oil pressure to the hydraulic zero-lash adjuster when the engine valve is closed.
In this invention, in a state where the engine valve is closed, an oil pressure in the hydraulic zero-lash adjuster is maintained to be relatively low since no compressing force is exerted thereon. Thus, by supplying an oil pressure to the hydraulic zero-lash adjuster in such a state, it is possible to reduce a required oil pressure to be supplied to the hydraulic zero-lash adjuster.
The above-mentioned second object of the present invention can be achieved by the solenoid valve device further comprising:
a current source which supplies a current to the electromagnet;
a current setting part which sets the current supplied to the electromagnet by the current source to be a value which is different from a value used in a regular situation for a predetermined period after the hydraulic zero-lash adjuster starts being supplied with an oil pressure.
In this invention, immediately after the hydraulic zero-lash adjuster starts being supplied with an oil pressure, the hydraulic zero-lash adjuster does not sufficiently expand. In this case, a position of the armature is shifted toward the engine valve as compared to a regular state (that is, a state in which the hydraulic zero-lash adjuster has expanded so as to cancel a clearance between the engine valve and the armature). On the other hand, a current to be supplied to the electromagnet to exert a required electromagnetic force on the armature changes in accordance with a distance between the armature and the electromagnet. Thus, according to this invention, it is possible to exert a proper electromagnetic force on the armature by setting a current supplied to the electromagnet to be a value which is different from a value used in a regular situation for a predetermined period after the hydraulic zero-lash adjuster starts being supplied with an oil pressure.
The above-mentioned second object of the present invention can also be achieved by a controller for controlling the solenoid valve device comprising:
a current source which supplies a current to the electromagnet;
a relative position detector which detects a value which is related to a relative position of the armature and the electromagnet; and
a current setting part which sets the current supplied to the electromagnet by the current source in accordance with the value detected by the relative position detector.
In this invention, a current to be supplied to the electromagnet is set in accordance with a distance between the armature and the electromagnet. Thus, according to this invention, since the current supplied to the electromagnet is set in accordance with a value related to a relative position of the armature and the electromagnet, a proper force can be exerted on the armature so that the engine valve can be positively actuated.
In this case, the value related to the relative position of the armature and the electromagnet may be a time which has elapsed after the hydraulic zero-lash adjuster stops being supplied with an oil pressure until the hydraulic zero-lash adjuster starts being supplied with an oil pressure.
In this invention, in a state where the hydraulic zero-lash adjuster is supplied with no oil pressure, the hydraulic zero-lash adjuster gradually contracts with a passage of time since oil leaks out from the hydraulic zero-lash adjuster. The relative position of the armature and the engine valve changes in accordance with the contraction of the hydraulic zero-lash adjuster. Thus, the time which has elapsed after the hydraulic zero-lash adjuster stops being supplied with an oil pressure until the hydraulic zero-lash adjuster starts being supplied with an oil pressure is related to the relative position of the engine valve and the armature.
Additionally, the value related to the relative position of the armature and the electromagnet may be an oil pressure which is supplied to the hydraulic zero-lash adjuster.
In this invention, an amount of expansion of the hydraulic zero-lash adjuster changes in accordance with an oil pressure supplied to the hydraulic zero-lash adjuster. The relative position of the armature and the engine valve changes in accordance with the contraction of the hydraulic zero-lash adjuster, as mentioned above. Thus, an oil pressure which is supplied to the hydraulic zero-lash adjuster is related to a relative position of the armature and the electromagnet.
The solenoid valve device may further comprise a failure detector which detects a failure in a system for supplying an oil pressure to the hydraulic zero-lash adjuster, wherein the value related to the relative position of the armature and the electromagnet is related to the failure detected by the failure detector.
In this invention, when a failure has occurred in the system for supplying an oil pressure to the hydraulic zero-lash adjuster, the oil pressure supplied to the hydraulic zero-lash adjuster decreases. An amount of expansion of the hydraulic zero-lash adjuster changes in accordance with the oil pressure supplied to the hydraulic zero-lash adjuster and a relative position of the armature and the electromagnet changes in accordance with an amount of expansion of the hydraulic zero-lash adjuster. Thus, the value related to a relative position of the armature and the electromagnet can be related to the failure in the system for supplying an oil pressure to the hydraulic zero-lash adjuster.
Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.